1. Field of the Invention
The present invention relates to an engine controlling apparatus and method for a car employing an electronically controlled throttle valve.
2. Background Information
One engine controlling apparatus is constituted so as to set an objective throttle opening degree by reference to a characteristic table indicating a relationship between the accelerator opening degree and the throttle valve opening degree, on the basis of detection of a present accelerator opening degree. The other engine controlling apparatus is disclosed in Laid-open Japanese Patent Publication No. 9-228867, which is constituted so as to control setting of an objective opening degree of the throttle valve by firstly calculating an objective engine torque on the basis of detection of a present, accelerator opening degree and by subsequently using the calculated objective engine torque to determine an opening degree of the throttle valve from the characteristic map of the throttle valve opening degree, in which map an objective engine torque and an engine rotating speed are parameters.
Moreover, either when the above-mentioned throttle valve opening degree characteristic map is set in the former case or when the calculation of the objective engine torque is carried out on the basis of the present opening degree of the accelerator in the latter case, it is possible to pay an additional consideration to a power performance of the engine, as required.
With regard to the subject of a power performance and an accelerating feeling of an engine-operated car, if a car driver is able to have a feeling of a rise in an output torque and an engine power in response to an increase in the car speed and the engine rotating speed, he will surely be able to perceive that the car is powerful. More concretely, for example, if each of the two driving conditions is satisfied, an engine can be considered as being sufficiently powerful. Namely, in the first one, when the car is started and shifted up to accelerate the car, even if the rotating speed of the engine drops down for a while due to the shifting up, when the driver can thereafter have a feeling of a rise in the output torque and power of the engine in response to an increase in car speed and engine rotating speed, he will be able to have the feeling of powerfulness on the engine.
In the other condition, during running at a constant speed on a road, i.e., during running on a 0% inclination road, when the accelerator pedal is pressed down and a shifting down is conducted so as to increase the engine rotating speed. If a rise in the output torque of the engine occurs in response to an increase in the engine rotating speed and the car speed, the car will surely provide a driver with the feeling of powerfulness of the engine.
Nevertheless, in the art of electronically controlling of the engine by using a micro-computing unit, e.g., a central processing unit (a CPU), on the basis of only the characteristic table between an opening degree of an accelerator and that of a throttle valve, an increase in a rotating speed of the engine cannot be further incorporated into the controlling factors, and accordingly it is impossible to produce and incorporate the above-mentioned feeling of the output torque of the engine in a controlling program for controlling the engine.
In addition, there is a non-linear relationship between the opening degree characteristic of a throttle valve and the output torque characteristic of the engine, that is, while the opening degree of the throttle valve is becoming large, an increase in the output torque comes to a saturation. Also, the above two characteristics change in response to a change in the engine rotating speed. Therefore, it is quite difficult to produce these characteristics in a controlling program for obtaining a desired power performance of a car. In other word, it is impossible to produce a linear rise in the output torque and power of the engine in a controlling program for controlling the engine.
Therefore, a primary object of the present invention is to provide a novel technical concept, which when an assumption is made that an output power of the engine is controlled by adjustably regulating a position of an electronically controlled throttle valve based on a set value of an objective engine output torque, allows to produce a controlling program including a rise in an output torque of the engine in response to an increase in the car speed and the engine rotating speed, by effectively correcting the set value of the objective engine output torque.
To this end, the present invention was made to adopt a constitution in which when an objective torque of a car engine is set to adjustably regulate an electronically controlled throttle valve to thereby control an output power of the engine, an amount of correction to be provided to an objective torque of the engine is calculated by performing a surface interpolation on a map in which the lattice axes are formed by a speed change ratio of a transmission and a rotating speed of a car engine, in respective directions of the axes of the speed change ratio and the rotating speed of the engine, and the calculated amount of correction is used for correcting the objective torque of the engine.